I. Field
The present disclosure relates generally to communication, and more specifically to cell measurements in asynchronous communication networks.
II. Background
Wireless communication networks are widely deployed to provide various communication services such as voice, packet data, broadcast, messaging, and so on. These wireless networks may be capable of supporting communication for multiple users by sharing the available network resources. Examples of such wireless networks include Code Division Multiple Access (CDMA) networks, Time Division Multiple Access (TDMA) networks, and Frequency Division Multiple Access (FDMA) networks. These wireless networks may also utilize various radio technologies such as Wideband-CDMA (W-CDMA), cdma2000, Global System for Mobile Communications (GSM), and so on, which are known in the art.
A terminal (e.g., a cellular phone) may be capable of communicating with multiple wireless networks such as a Universal Mobile Telecommunication System (UMTS) network that implements W-CDMA and a GSM network. Each wireless network typically includes many cells, where the term “cell” can refer to a base station or the coverage area of the base station, depending on the context in which the term is used. The terminal typically communicates with a serving cell in only one wireless network at any given moment but may periodically make measurements for cells in the other wireless network. The cell measurements may include measurements for received signal strength, frequency, timing, and identity of the cells. The cell measurements allow the terminal to ascertain whether any cell in the other wireless network is better than the current serving cell. If a better cell is found in the other wireless network, then the terminal may switch to the other wireless network and receive service from the better cell.
It is desirable to make the cell measurements as quickly and efficiently as possible. For example, the terminal may be mobile and may have moved outside the coverage of the serving wireless network. By completing the cell measurements and reporting the better cells sooner, the terminal may be handed off to a better cell before the call is dropped. However, the GSM and UMTS networks may operate asynchronously so that the timing of the cells in the GSM network cannot be ascertained based on the timing of the cells in the UMTS network, and vice versa. Furthermore, the cells in each network may operate asynchronously of one another. The asynchronous operation at the network and cell levels complicates cell measurements.
There is therefore a need in the art for techniques to efficiently make cell measurements in asynchronous communication networks.